The DNA Microarray and Homology Modeling Core will have several major functions. First it will be a resource for laboratories to examine how exposure to toxic agents affects gene expression. Laboratories will discus with Core personnel (Project Leaders, Senior Investigators, or PGR) projected experiments so that practical plans can be developed. Such discussion will lead to discussions whether a given problem is addressed best (a) by generating a limited cDNA array by subtractive hybridization, (b) using a subset of cDNAs available in the Core repository, or (c) through a full array of cDNAs available in the repository. When a subtractively hybridized array is considered the appropriate approach, the Core will assist in its generation by representational difference analysis, a technique with which Dr. Gregg (Senior Investigator) has much experience. As the Core expands its repository of cDNA clones, the emphasis is anticipated to shift gradually to larger arrays. This will be true particularly in the case of human genes, for which we already have at our disposal nearly 10,000 clones through the effects of Dr. Wu (Senior Investigator) and colleagues. The Core will prepare arrays for Superfund experiments, conduct the hybridization and scanning, present the results to the labs and help with the interpretations. A second major function of the Core will be in 3-D homology modeling. This will permit Superfund investigators to examine protein-toxicant interactions electronically, thereby gaining valuable mechanistic information that can be applied to other potential targets. The third major junction of the Core is in bioinformatics. This will consist largely of data management, assisting Superfund investigators with data analysis and database searchers and helping investigators utilize the campus Life Sciences Informatics Program. Initial data handling will be in this core. As data sets become larger they will be transferred to the Statistics Core B.